Packed column distillation apparatus

ABSTRACT

Apparatus is provided for converting sea or other undrinkable waters to drinkable water without the use of driven or moving parts. Reliance upon gradient effects is made to effect the vaporization of, for example, sea water, followed by the condensation of the vapor to form distilled water. Gradient effects are achieved through the provision of differentials in the thermal conductivity, capillary activity, adsorptive, absorptive and/or pressure characteristics of particulate materials, or combinations of such physicals. For example, a column is packed with material graded as to its conductivity, the least thermally conductive material being nearest the cold or ambient water that is to be purified. In packing the column each successive layer of material has a greater thermal conductivity than the layer beneath it with the most conductive being at the top near the outlet arm of the column. The final outlet arm or tube is unheated or is at a temperature lower than that of the topmost conductive material so that vapor reaching the outlet tube gets condensed. This tube leads to a container kept in a cool place as, for example, buried in the ground, as, for instance, at the seashore deep enough to be cooled or to be surrounded by water, thus keeping the condensate cold. Pure water so collected is removed by such means as is desired. Other impure, volatile liquids may be similarly purified.

This is a division of my application Ser. No. 110,636, filed Jan. 9,1980 and now U.S. Pat. No. 4,326,923.

BACKGROUND OF THE INVENTION

The energy sources of the world are currently not being adequatelydirected to the urgent need for many peoples of the world to have decentwater and ample supplies of it. Further, there is considerable concernas to the quantities of fuels and the effect on the world and itscreatures through the use of the fuels. Therefore, there is a resurgenceof interest in the use of solar energy. As a result many publicationsare issuing. Among these dealing with the production of potable waterare the following U.S. Pat. Nos.: 4,078,975; 4,075,063; 4,062,735;4,053,368; 4,010,080; 3,785,931; 3,428,529; 3,414,481; 3,359,183;3,357,917; 3,357,898; 3,351,538; 3,338,797; 3,300,393; and 3,135,466. Anexamination of the prior art will reveal a considerable diversity inapproaches. Quite a number use moving parts or require energy other thansolar energy. While there are a number of devices that use no movingelements, it is believed that hithertofore no one has applied gradienteffects to produce a vapor and reverse gradient effects to condense itto the liquid state in the manner of this invention.

It is, thus, an objective of this invention to effect the distillationof water from a non-potable or other source to produce a distilled waterwhich is potable. Another aim is to effect an increase gradually in thetemperature of a liquid or in its purity, to the point where one pureliquid vaporizes or advances and then gradually to reduce itstemperature to the point where vapor becomes or is maintained as liquid.A still further purpose is to effect the aforesaid changes by usingmaterials varying in their thermal conductivity and/or varying in theircapillary effects. These other objectives of this invention appearhereinafter.

BRIEF DESCRIPTION OF THE INVENTION

The above objects are accomplished, for example, by the provision of acolumn which is packed with a variety of materials each of which ischosen to have a greater thermal conductivity than the adjacent materialbelow it. Since the column is placed at its inlet end in contact withthe liquid to be purified and that liquid is normally at ambienttemperatures, the first material placed in the column is a materialwhich is a poor conductor of heat. In the case of converting salt water,such as ocean water, to potable water, that material is normally sand.Above it may be placed a mixture of sand and a heat conductor such aspowdered copper with the mixture being mostly sand. Above that layer isplaced a similar mixture having less sand and more metal, as, forexample, a 60/40 mixture of sand/metal. That is followed successively bya 50/50, then a 40/60 and the like, the top-most layer being 100% metalin particulate form.

It is to be understood that the materials are placed in a tubular or thelike, elongated container which is equipped with a side arm forconveying condensate to a receptacle. The container may be unitary orconstructed of segments. In its unitary form, it is covered with heatabsorbent materials which vary in their thermal conductivity in asimilar manner as the particulate materials within the container. Thus,the covering materials are better and better heat conducting elements asone goes from the inlet or bottom of the elongated container toward itsoutlet or top. If made of segments, the same is true, the bottommostsection being a poor conductor of heat, being made, for example, of asynthetic polymer or concrete and the topmost being metallic.

In order to keep the condensate in liquid form and to facilitatecondensation, the side arm or condensing part of the distillationapparatus is constructed entirely of a poor thermal conductor or iscovered or segmented to produce a gradient in thermal conductivity goingfrom excellent conductivity in the area where the side arm is joined tothe elongated column to poor thermal conductivity where the sidearmdelivers the condensate to the receptacle. Such a vessel is normallymade of a thermal non-conductor and can be buried in the ground. Anoutlet in it and a pumping element afford removal of the condensate.

The invention will be further understood by reference to the drawingsand the detailed description below, all of which is given forillustrative purposes only and is not limitative. The drawings are asfollows:

FIG. 1 is a sectioned view of the distilling column illustrating theaforesaid gradients in the elongated column;

FIG. 2 is a front elevation showing the column covered with insulationand showing the gradation of light absorption effected by shading to noor a very slight extent upwardly to a heavily darkened exterior; and

FIG. 3 taken on 3--3 of FIG. 1, is a cross-section of the column showingan additional embodiment for effecting conductance of heat to the backside of the column that is not exposed to solar energy.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1, an elongated container 10 is placed directly in theliquid to be distilled, such as the designated salt water 11a adjacentto land 11. The outside wall of container 10 may have extensions 12 atthe bottom to support the apparatus as shown in FIG. 1 or othersupporting means may be used, as, for example, stays or guy wirescommonly used in supporting trees, telephone poles and the like. Anyeconomical, effective supporting means may be used, of course, and suchwill be chosen with weather conditions of the locale in mind, as well aswith the size and weight of the materials being used. Usuallylightweight, weather durable materials are used. The elements of thisinvention which become in contact with or exposed to salt water orcorrosive materials, such as supports 12, or lowermost screen 15 ormembrane 24, are constructed of inert materials such as inert metals,concrete, or inert synthetic polymers such as poly(tetrafluoroethylene).

The bottommost part of container 10, designated as 13 in FIG. 1, isgenerally constructed of a poor conductor of heat such as concrete or asynthetic polymeric material. This supporting means, section 13 isperforated, as, for example, being slotted as indicated by the arrows 14to allow the liquid to reach and contact the bottommost layer ofpulverulent material A. This material is generally sand, and it rests onscreen or porous element 15 which is usually a strong copper or the likescreen or perforated plate having a mesh considerably smaller than theparticle size of material A. Resting on top of layer A is a layer ofparticulate material B which has a greater ability to conduct heat thandoes A, for example, by being a mixture of sand and a powdered metalsuch as copper. Similarly, layer B is topped by an even better conductorC, which is in turn topped by a still better conductor D. Thesegradients can be effectively and economically gotten by simply loweringthe amounts of sand and increasing the metal content as one goes fromlayer to layer, ending normally with layer E which contains but littlesand and with layer F which is all pulverized metal. If desired, ascreen element 15 may be placed on top of each layer and may be fixed toor supported by the inner walls of the column. Such placement preventsundesirable shifting of materials downwardly. Generally, a screen ispositioned at the top of the uppermost layer (F) to prevent carryover ofsolids into side arm 16.

The very top of container 10 is sealed as at 17. Since solar energy isbeing used to effect the heating of the pulverulent materials insidecontainer 10, heating element 18 may be provided at closure 17 to assistin keeping vapors that reach this area in the gaseous state. Element orvane 18 can be of any convenient size and shape and is generallyconstructed of metal such as aluminum or copper. One, of course, avoidsthe use of the rust-forming irons or of readily oxidizable metals.

The condensation section 16 of the still is generally made of anon-conductor, being, for example, a tube of poly(tetrafluoroethylene).It terminates in sealed relationship with receptacle 19, also made of anon-conductor and, if at a seashore, generally buried in the sand, deepenough to be surrounded by water as a further way of effectingtemperature differentials and keeping the condensate cold. This is shownin FIG. 1 which also shows element 20 as an outlet for the condensate,pumping elements being omitted for convenience, outlet 20 also providingaccess to atmospheric pressure as a lower pressure than that whichbuilds up within column 10.

From the above it will be understood that the sun's rays upon strikingthe outer walls of container 10 will heat them and that heat will beeffectively conducted inwardly since the layers of particulate materialare in contact with the inner surfaces of the walls. The inward flow ofheat will be greater the greater the thermal conductivity of the givenlayer. Therefore, a temperature gradient is created within container 10,the temperature getting higher and higher as the approach to the sectionabove layer F becomes shorter. Temperatures exceeding the boiling pointof water may thus be reached. With the vaporization of water, whether byboiling or otherwise, the pressure within the container 10 exceedsatmospheric pressure so that a continuous sweep of vapor passes intocondenser 16 to appear as liquid 21 in vessel 19 as indicated by arrow22.

In addition to or instead of graded materials A to F inside the column,one may effect a thermal gradient by wrapping or covering element 10with heat absorbent material outside. The absorbent material is made toincrease in amount as shown by the shading in FIG. 2. This representsthe use of an increasing amount or thickness of insulation material,such as fiber-glass or, alternatively, the covering material varies fromsection to section in the efficiency of the heat-absorbent materialselected without the need of adding substantial weight. Thus, thelowermost section above the surface 11b of water-body 11a may be paintedwith a white paint with successively higher sections being painted withincreasingly darker paints with the topmost being a black paint.Alternatively or additionally, the paints may contain increasing amountsof thermal-conducting materials such as pulverized metals such asaluminum, black nickel, zinc, copper, copper oxide and nickel oxide.

Similarly, the condenser 16 may be covered with heat-reflectivematerials such as aluminum wrap or paint with the reflective ability ofthe coating or wrapping material increasing in efficiency or quantitythe closer the condensate gets to receptacle 19. In other words, asindicated at 28, the section of condensing arm 16 nearest column 10 willbe the most heat retentive in order to minimize heat loss in thecontiguous part of column 10 while the section of arm 16 nearestreceptacle 19 will be the least heat retentive or the more reflective inorder to get as much cooling of the condensate as possible.

While one may, of course, use mirrors or the like to concentrate rays ofthe sun on particular portions of element 10, the need for such is notnecessary and is advantageously obviated by the principles of thisinvention. The various materials used in constructing and operating thestill of this invention are readily available and inexpensive. No movingparts are employed in effecting the distillation. A continuous processis effected. Further, the materials are long lasting.

The container or column 10 may be entirely constructed of concrete orsimilar masonry and may be of any desired length and other dimensions.It need not be vertically positioned as in FIG. 1 but may be angularlypositioned to achieve optimum insolation. The outlet tube 16 may extendupwardly over considerable distances to permit the collection of purewater remote and above the level of the impure water at 11a. Gravityflow from receptacle 19 is then possible to effect direct flow of waterto people or to turbines or the like for energy conservations.Extensions of tube 16, will, of course, create heat-loss possibilities.Therefore, the principles of this invention are again applied to anysuch extensions. In other words sections or all of such an extension maybe provided with the gradient-producing materials described for and incolumn 10 until the final outlet arm or tube is reached at which areathe attainment of the above-described reverse gradient effects isprovided for by use of said reflective elements.

While it is possible, as stated above, to associate column 10 and/oroutlet tube 16 with reflectors, such as mirrors or polished sheets ofsuch metals as aluminum or a chromium plated metal and to activate suchso that they track the sun, it is preferred to minimize, and to avoidentirely the use of power other than that of the sun's rays. Thus, theprinciples of this invention may be applied in a supplementary manner tothe dark side of the stationary column. One skilled in the art willdetermine quite accurately the area that receives no sun's rays. Thatarea is then covered with, for example, a thermally conductive paint,such as an aluminum paint to a desired thickness or adhered to the outersurfaces in that area of column 10 are metallic sheets or strips 21which extend into a portion of the area where the sun's rays arestriking. Such metal elements can be mounted through the use of threadedstuds and nuts, not shown for convenience, or are adhesively bonded to10. In any event, this element, shown in FIG. 3, may be applied allalong the dark side of column 10 with insulation 26 placed over theconductive materials used. The latter is generally used in increasingamounts going away from the bottom of the column but the insulatingmaterial is generally of uniform thickness though it may be thicker atthe hotter areas. In some locations, as for example in hot desertregions, there may be no dark side due to the reflective surroundings.Then, of course, the above elements need not be used. The insulation maybe made of asbestos, fiberglass, contained vermiculite, styrofoam,polyurethane and the like.

Similarly, the outlet arm 16 will have a dark side. Here again, thoseareas may be treated as above with the area of the dark side adjacent toreceptacle 19 being not so treated, or being on all sides coated with orbearing a highly reflective material or being jacketed for the receptionof cold water as in conventional distilling columns. Cooling water maybe taken from receptacle 19 and returned. This arrangement is shown inelevation by lines 23. Water is pumped out of container 19 by pump P andis passed to condenser or jacket 23 from which it returns to container19.

Prior to being sent to container 19, the hot vapors coming into outlettube 16 may also be directed against a vessel containing a low boilingliquid, such as a hydrocarbon like isobutane or pentane or a halogenatedhydrocarbon, such as monofluorotrichloromethane, to vaporize it,directing such vapors to run a turbine. The said hot vapors are thencondensed and sent to receptacle 19.

The placement of receptacle 19 in a cold or relatively cold place, asunderground and surrounded by water, is advantageous in that thereceptacle itself acts as a condenser. The flow of vapor into it isunder pressure and seeks the outlet 20. Since the inner walls of 19 arecolder than the incoming vapor, condensation occurs. If desired, theceiling of 19 and/or its walls may be slanted, and the exit orifice ofoutlet arm 16 may be so placed to jet the incoming vapor and/orcondensate against such slanted inner surfaces to facilitatecondensation.

In any event there is a pressure differential between outlet 20 and theentrance of the impure water into column 10. Sea water and bodies ofimpure water contain varying amounts of air. Thus, air is passingthrough the system along with the vapor of the liquid being purified, inthis case, water. That flow may be increased by tapering column 10 withthe smallest dimension of it near outlet arm 16 and by tapering thelatter with the smallest dimension at receptacle 19. The outlet or vent20 in container 19 may be similarly tapered. The velocity of the flow ofgaseous material is generally commensurate with the condensation that isoccurring so that flooding of column 10 usually does not occur.

A pressure differential in addition to that just described and to thatoccurring as a result of placing receptacle 19 high above column 10 assuggested in the FIG. 1 by broken lines 27, the drawing not being toscale, is created by placing a permeable membrane 24 on screen or porouselement 15. This porous or permeable member may be made of any of alarge number of materials cellulose acetate and any of many syntheticpolymers in film form such as polyvinyl chloride, polypropylene,polyethylene, the polyurethanes, cellulose derivatives such as cellulosebutyrate and nylon, the polyimides, tetrafluoroethylene polymers, andits co-polymers, the poly (tetrafluoroethylenes), thepoly(tetraethyleneterephthalate) polymers among others. Any of thesealso can be used as screen element 15. Screens 15 and membranes 24 aresnugly fit or are bonded to the inner walls of column 10 so as to be insealing relationship with those walls and in the case of the membranesto be in sealing relationship with the impure liquid material downstreamand in feeding relationship therewith to pass said material upstream.

The concentration of the salt in sea water is generally low being abouta few parts per million to about 3 to 4% and that of impotable waterbodies, such as salt marshes, is also low. The semipermeable membrane 24prevents the passage of the salts in the impotable water into column 10.In order to increase the flow of water through the membrane, a layer ofrock salt 25 or other salts may be deposited initially on top of saidmembrane, or the bottommost layer A may be a mixture of salt and sand sothat there is within column 10 at the bottom a salt solution greater inconcentration than that in the water being purified. The use of such agradient is advantageous in that a buildup of salt within the column isprevented.

This prevention is particularly important when capillary gradients aresubstantially relied upon. The capillary lifting of water by, forexample, sand in layer A is greater than the capillary lifting of alayer of a particulate metal, as in layer F. Since an objective of thisinvention is to get pure water up into the upper sections of column 10,the capillary effectiveness of the layers can be increased by usingpulverulent materials such as natural or synthetic zeolites, pumice,pulverized limestone or lava, other synthetic materials such as silicagel and porous polymers such as those named above. Organic capillaryeffective materials include cellulose materials such as cotton, woodpulp or sawdust and the like, charcoal, or peat moss. Such materials maybe used alone or admixed into sand in layer A, and in successivelydecreasing amounts in the layers above, as in layer B and C. Generally,capillary activity is not needed in such layers as D and E, for therethe evaporation of the liquid is occurring smoothly if solar energy isbeing used. In any event, the use of such capillary active materialsdoes not require washing them out with salt free materials if membrane24 is used. If the capillary gradient principle is not used, suchwashing is not needed either, because the capillary activity of sand andthe sand mixtures is not great enough to cause salt build-up within thecolumns not only because of the lower effectiveness in pick-up of liquidbut because of the constant flow into and out of column 10 of sea waterat the bottom of column 10 through passageways 14.

The abovementioned capillary materials may be mixed with the thermalgradient mixtures described above in improving the efficiency of thecolumn when solar power is low or absent. While the column 10 may bepacked solely with capillary gradient material, it is preferred to usethermal gradient materials with them to increase flow rates.

By this invention a passive system is provided for converting impotablewater from such sources as rivers, seas, oceans, swamps and the like topure water. No moving parts are needed. There is no consumption of oil,natural gas, electricity or coal or the like. Further, the conversionmay be effected without requiring the production of temperatures neededto boil water though such are attainable. Through the use of easilyproduced gradients a flow of air is made to occur. Thermal, capillaryand pressure gradients are used cooperatively to separate a liquid,water or other liquids, from contaminants, to convert the liquid in sodoing to a vapor, to cause that vapor to move through zones involvingthermal gradients and to be condensed into pure liquid. The apparatusneed not be positioned in the exact vertical but may be inclined or evenused horizontally.

All of the materials used are inexpensive or of moderate expense and arereadily available. For example, 50 gallon steel drums may be used byperforating the bottoms and stacking one upon the other to form sectionsA to F and welding or otherwise supporting the sections. These sectionscan be removably mounted or can be equipped with access doors for readycharging or recharging their contents. The materials used should be ormade to be substantially resistant to the effects of salt water or hotwater. The principles of this invention may also be applied to therecovery of or the purification of industrial water or other industrialwastes.

For example, organic solvents, such as acetone, benezene or toluene, maybe recovered by use of the process and apparatus of this invention. Suchorganic materials may be separated from dissolved or suspended solidmaterials therein, such as catalysts and polymeric materials at theplant site so that they can be used immediately in subject plantprocesses. Also, by properly selecting screen 15 or permeable membrane24 one may separate liquids from liquid. Use of a membrane permeable tobenzene vapor but impermeable to water vapor, such as a film of apoly(tetrafluoroethylene) polymer, affords ready recovery of drybenzene. In effecting such separations by using solar energy and theprinciples of this invention one skilled in the art need only to selectthose pulverulent materials which are resistant to attack by thenon-aqueous materials being processed.

The majority of the devices and methods of this invention are, ofcourse, dependent upon solar energy, but this is but a universalobstacle of man. In this context, a great advantage of this invention isthat the construction and operation of the equipment are so simple thatvirtually any man can build the apparatus and attend to its maintenance.

While the invention has been disclosed herein in connection with certainembodiments and certain structural or procedural details, it is clearthat changes, modifications or equivalents can be used by those skilledin the art; accordingly, such changes within the principles of thisinvention are intended to be included within the scope of the claimsbelow.

I claim:
 1. Apparatus for the purification of an impure volatile liquidwhich apparatus comprises a distilling device comprising a column and acondenser;in said column a capillary gradient comprising a columnpacking material varying in capillary activity, material of relativelylow capillary activity being in closest position within said column tosaid impure liquid with capillary material of successively bettercapillary activity being above it to form said gradient with materialhaving the best capillary activity near the outlet of said column tosaid condenser, said material being substantially unchanged by contactwith said impure liquid; and said condenser comprising means to convertany vapors from said liquid to a purified state.
 2. Apparatus inaccordance with claim 1 in which said capillary active materialscomprise naturally occurring organic materials.
 3. Apparatus inaccordance with claim 1 in which said capillary materials comprisenaturally occurring inorganic materials.